1. Field of the Invention
The present invention relates to a blocked polyisocyanurate and polyvinyl chloride plastisol compositions (hereinafter referred to as "PVC plastisol compositions"), containing the same as an adhesiveness providing agent. More specifically, the present invention relates to a blocked polyisocyanurate having resistance to discoloration and suitable for use as an adhesiveness providing agent, coating material, sealant, crosslinking agent for polymers containing active hydrogens and the like, and also relates to polyvinyl chloride plastisol compositions having high adhesiveness even when cured at low temperatures and resistance to yellowing, which contain the above polyisocyanurate as an adhesiveness providing agent and which are particularly suitable as sealants for car bodies.
2. Descriptions of the Prior Art
In recent years, PVC plastisol compositions have been used in a wide variety of fields, such as adhesives, sealants, covering materials and the like.
There are known PVC plastisol compositions, for example, one comprising polyvinyl chloride resin, a plasticizer and, as an adhesiveness providing agent, a long-chain alkylphenol-blocked polyisocyanate (see Japanese Patent Application Laid-open No. 41278/1987). According to the application, this plastisol composition has high storage stability under conditions of high temperature and high humidity, is free from foaming or discoloration and can form at high temperature a gel having high adhesiveness.
The above conventional PVC plastisol composition has, however, been found to be of poor adherence when cured at a low temperature in the range of 110.degree. to 130.degree. C. on electrodeposited base materials.
As a result of an intensive study to overcome this problem, the present inventors have found that PVC plastisol compositions, that can be hydrolyzed by moisture present in the system or in the air even at such a low temperature as the above range to be cured while exhibiting good adhesion to base materials and do not yellow after the curing, are obtained by using an adhesiveness providing agent comprising a specific polyisocyanate being blocked with styrenized phenol and being capable of dissociating by de-blocking even when cured at this low temperature, together with a specific dissociation accelerating agent. The present invention has been completed based on this finding.